1. Field of the Invention
The present invention relates to a method of manufacturing containers for dispensing solutions and, more particularly, to a method of manufacturing transfusion containers by blow molding, without causing contamination of a charged medical solution with impurities.
2. Description of the Prior Art
Heretofore various methods have been used for manufacturing containers for dispensing solutions, such as transfusion containers. A primitive method comprises the steps of sealing two sheets of thermoplastics with heat along three sides thereof to form a container and providing an opening of the remaining sides of the resultant container with a mouth member for sealing the produced container. Another method comprises the steps of sealing one open end of a tubular member of thermoplastics with heat and then providing the other open end thereof with a mouth member for sealing the produced container. Another method is a blow molding technique in which a container is directly produced from thermoplastic resins. Among them, the blow molding is now widely used as it has an advantage such that a produced container can be filled with a medical solution and then sealed with the attachment of a mouth member during manufacture of containers for dispensing solutions.
However, the blow molding of the prior art requires use of a complex device since both the blowing and charging steps must be carried out with a blowing mandrel provided with a charging nozzle. For example, as illustrated in FIG. 9, the blow molding equipment of the prior art comprises a blowing mandrel 600 and a reciprocating charging core 603 coaxially arranged therein and movably supported by packing 604. The charging core 603 is closed by a valve 601 with a sealing packing 602 during formation of a container but opened when injecting vapor, washing liquid or air into a produced container.
Such a structure makes the molding equipment complex in structure and increases the diameter of a mandrel, which in turn causes a limit on the head shape of containers to be produced and makes it difficult to perform fine control of the molding conditions. Also, it takes a long time for maintenance of the device. In addition, there is a fear of contamination of charged medical solutions with dusts resulting from wear or degradation of the packing since the reciprocating charging core has to be held in the mandrel and sealed by the packing 604 to avoid leakage of vapor, washing liquid or air into the core.
In addition, in the blow molding of the prior art the inflation has been carried out by cutting the parison after inserting it into the mold, the parison may come into contact with the inside of the mold, which causes whitening of the surface of the produced container.